The long-term goals are to reify new, non-invasive methods for quantifying the optical quality of the eye's retinal image from wavefront measurements and determine the relationship between retinal image quality and visual performance. The specific aims of this competitive renewal are to: 1. Test the ability of our new metrics of retinal image quality to detect change in optical disease. 2. Directly test the organizing hypothesis that a change in retinal image quality is predictive of future vision loss in optical disease. 3. Improve the power of newly developed single-valued wave aberration metrics to predict a change in visual performance by adding measurements of forward scatter. 4. Use physical and computer models to test the measurement assumptions of our new analysis of forward scatter and explore ways to improve the speed, efficiency and accuracy of our analysis. These specific aims will be accomplished by: 1. A 5-year longitudinal study of 120 patients with cataract, monitoring visual performance and retinal image quality using metrics of aberration and scatter derived from Shack/Hartmann wavefront sensing. 2. Analyzing the data to test whether our metrics can detect change over a short time period that is predictive of future loss and in the process continually improve our metrics. 3. Building both wave aberrations and forward scatter into physical and computer models to test measurement assumptions and explore ways to improve our analysis. This line of research will advance the fundamental understanding of retinal image quality and its relation to visual performance and provide a sensitive method for assessing the optical quality of the eye and monitoring therapy designed to improve the optical quality of the eye.